The field of the disclosure is contact lenses formed from copolymerization of a hydroxyalkyl methacrylate with a HEMA-compatible bifunctional polysiloxane.
2-hydroxyethyl methacrylate (HEMA) is a biocompatible, polymerizable monomer that has been used for over the past forty years to make soft hydrogel contact lenses. HEMA-based hydrogel contact lenses are much more comfortable to wear than their rigid predecessors. However, a drawback of the HEMA-based hydrogel lenses is that they have low oxygen permeability. It was recognized that materials that provide higher oxygen permeability would be healthier for the cornea. In the late 1990s silicone hydrogel contact lenses, which have significantly higher oxygen permeability than HEMA-based hydrogel lenses, were introduced to the market. However, the siloxane monomers used to make silicone hydrogels are typically much more expensive than HEMA. In addition, the methods used to make silicone hydrogel contact lenses are substantially more complex and labor-intensive than for HEMA-based hydrogel contact lenses. It would be desirable to combine the benefits of HEMA with the oxygen permeability attributes of silicone hydrogels, however HEMA is very hydrophilic and is generally not miscible with silicone monomers.
Background publications include U.S. Pat. No. 8,053,544, U.S. Pat. No. 8,129,442, U.S. Pat. No. 4,260,725, U.S. Pat. Publ. No. 2011/0181833, U.S. Pat. Publ. No. 20060063852, and U.S. Pat. Publ. No. 2011/0140292.